Calibrated airflow measurement system for a ceiling vent

ABSTRACT

The disclosure is a calibrated airflow measurement system for measuring air flow through a ceiling vent having a moveable vane. The airflow flows through the ceiling vent in laminar flow into a ceiling. This allows the moveable vane of the ceiling vent to be reversibly responsive to airflow through the room and allows for the vent to be calibrated to disperse a predetermined amount of air into the room.

PRIORITY/CROSS-REFERENCE TO RELATED APPLICATIONS

This application hereby incorporates, by reference, U.S. Pat. No.5,261,857, entitled, “Ceiling Vent with Movable Vane.”

FIELD OF THE INVENTION

This invention relates to an improvement in a ceiling vent fordispersing airflow into a room. More particularly, the invention relatesto an airflow measurement system for determining outflow from a ceilingvent for adjusting the ceiling vent outflow level.

BACKGROUND OF THE INVENTION

Perhaps the most critical component of a heating or cooling system in ahome or office is the vent or diffuser for dispersing the heated orcooled airflow as evenly as possible throughout the room. If diffusionof the airflow throughout the room is uneven, then pools of air ofdifferent temperatures may form at various locations in the room. Thisis an inefficient way to heat or cool a room and can be uncomfortable topersons who live or work there.

The best known way to diffuse airflow in a room is to redirect theairflow in a laminar flow at the top of the room. This sheet of airflowthen mixes with the ambient air to achieve relatively even heating orcooling without pooling or dumping in certain locations. The distancethat airflow moves at a given velocity, or airflow throw, will vary withthe velocity of the airflow that moves through a vent. Thus, differencesin velocity will affect the evenness of air dispersion in a room. It ishighly desirable to maintain constant the airflow throw from a vent,despite variations in initial airflow velocity, to control the evenmixing of airflow in a room. A fluid, such as a current of airflow thatis moving at some velocity along an adjacent surface tends to cling tothat surface. This is because low pressure is created below the current,in the case of a stream of airflow moving along a ceiling, thus liftingthe current of airflow upward against the ceiling. This phenomenon, theCoanda effect, increases the airflow throw and thus, the dispersion ofair in a room.

One proposal for maintaining even mixing of airflow from a ceilingdiffuser involved a device mounted on conventional ceiling tee bars andcontaining a thermostatically controlled motor to position airflowcontrol vanes to manage variable flows of conditioned air (U.S. Pat. No.3,848,799). Another device handled variable airflow by pumping air intoa bladder to regulate the area of air discharge (U.S. Pat. No.3,434,409). Other devices of general interest had to be manuallyadjusted to handle different airflows (U.S. Pat. Nos. 4,475,446 and4,008,653). These devices all suffer the disadvantages of mechanicalcomplexity or the need for manual adjustment to handle variations inairflow.

Accordingly, applicant and co-inventors invented the device disclosed inU.S. Pat. No. 5,261,857, entitled “Ceiling Vent with Movable Vane”. Thevane of that invention is normally biased toward an airflow catch whichcomprises a partition also positioned in the path of inflowing airflowto redirect and laterally diffuse airflow within the plenum. When thereis no flow of airflow through the vent, the vane is disposed against theairflow catch to close the airflow discharge aperture. When airflowflows through the vent, the vane is moved away from the airflow catch bythe force of the moving airflow to variably adjust the width of theairflow discharge aperture. Both the movable vane and the airflow catchare curved to redirect the flow of airflow in a horizontal direction asit leaves the vent. The airflow catch also circulates airflow within theplenum to disperse it toward the edges of the airflow current andhomogenize the current velocities.

The problem associated with the applicant's previous invention is that,in order to calibrate the system of ceiling vents found in U.S. Pat. No.5,261,857, a vent adjuster or a team of vent adjusters would be requiredto come and calibrate each of the vents individually. In order to dothis, a hood is typically required to be put over each of the vents inorder to calibrate the amount of air flowing out of the vent. This wasrelatively expensive and required time to calibrate the system.Accordingly, a system is needed that reduces the amount of time andmoney to calibrate the system and allows for easier calibration andrecalibration of the system after the system is installed.

SUMMARY OF THE INVENTION

Accordingly, an improved ceiling vent having an airflow measurementsystem for dispersing airflow into a room in laminar flow with respectto the ceiling of the room has been invented. The airflow is typicallywithin a ventilation system of a building. The ceiling vent has a venthousing configured to be mounted in a ceiling. The vent housing definesa plenum on the inside of the housing. The vent housing has at least twoopenings; at least one of the openings allows for air to flow into theplenum of the vent housing and at least one of the openings allows airto flow out of the airflow vent in laminar flow along the ceiling of theroom in which the vent is mounted. The vent has a vane that generallyhas a concave curvature along its length. The vane is hingedly attachedto the interior of the vent housing such that the vent moves in reactionto airflow flowing through the plenum of the vent. The vane isconfigured to be reversibly responsive to the airflow against theconcave curvature of the vane and into the plenum. This varies the sizeof the opening into the room with the movement of the vane by theairflow while maintaining a curved flow path discharging the airflow inlaminar flow along the ceiling. The airflow measurement system ispositioned and configured such that when the vane position responds toairflow through the vent, the airflow measurement system indicates theoutflow level of airflow out of the vent such that the vent can becalibrated to distribute a prescribed amount of airflow into the room.The airflow measurement system comprises a calibrated scale havingairflow indicia in one embodiment. Furthermore, the calibrated scale canbe located such that the vane points to one of the airflow indicia onthe calibrated scale when airflow travels out of the second opening inthe vent housing.

The vent can also have an airflow catch such that the airflow catchpartitions airflow traveling from the inflow opening in the vent housingtoward the second opening. This facilitates mixing of airflow in theplenum. Additionally, the moveable vane can be configured to becalibrated to define airflow through the plenum. The ceiling vent canalso have a means for biasing the moveable vane toward the vent housing.This means for biasing the moveable vane can comprise a spring or weightattached to the movable vane that biases the vane toward the generallyclosed position. The second opening can comprise a wide variety ofopening shapes; in one embodiment it comprises a slot in the bottom wallof the housing.

The purpose of the Abstract is to enable the public, and especially thescientists, engineers, and practitioners in the art who are not familiarwith patent or legal terms or phraseology, to determine quickly from acursory inspection, the nature and essence of the technical disclosureof the application. The Abstract is neither intended to define theinvention of the application, which is measured by the claims, nor is itintended to be limiting as to the scope of the invention in any way.

Still other features and advantages of the claimed invention will becomereadily apparent to those skilled in this art from the followingdetailed description describing preferred embodiments of the invention,simply by way of illustration of the best mode contemplated by carryingout my invention. As will be realized, the invention is capable ofmodification in various obvious respects all without departing from theinvention. Accordingly, the drawings and description of the preferredembodiments are to be regarded as illustrative in nature, and not asrestrictive in nature.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a perspective view of a ceiling vent having a movable vane,an airflow catch, and an airflow measurement system mounted in asuspended ceiling, in accordance with the present invention.

FIG. 2 shows an end elevational view of a ceiling vent having a movablevane, an airflow catch, and an airflow measurement system mounted in asuspended ceiling, in accordance with the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

While the invention is susceptible of various modifications andalternative constructions, certain illustrated embodiments thereof havebeen shown in the drawings and will be described below in detail. Itshould be understood, however, that there is no intention to limit theinvention to the specific form disclosed, but, on the contrary, theinvention is to cover all modifications, alternative constructions, andequivalents falling within the spirit and scope of the invention asdefined in the claims.

Referring to the drawings, FIG. 1 shows a ceiling vent 10 mounted in asuspended ceiling 12. The ceiling vent 10 is not limited to mounting insuspended ceilings, however, and may be mounted in other ceilings, suchas a gypsum board ceiling 14 as in FIG. 2. The ceiling vent 10 comprisesa plenum 16 and a housing 18. The housing 18 may be insulated tominimize changes in temperature of the airflow as it flows through theceiling vent 10. In the preferred embodiment, a wall of the housing 18has an opening 20 through which a current of heated or cooled airflow 22a and 22 b enters the plenum 16 from an airflow and plenum source.Connected to and extending outward from the housing 18 and surroundingthe opening 20 is a sleeve 24 for connecting the ceiling vent 10 to aduct that conducts heated or cooled airflow from the source.

Attached to the inside of the housing 18 is a movable vane 26 which isan elongate curved sheet that is hingedly suspended at one end of themoveable vane from the housing 18 at a hinge point 28. This vane 26 ispositioned in the housing to receive the force of the inflow of airflowinto the plenum 16. The bottom of the housing 18 contains a slot 30 fromwhich airflow exits the ceiling vent 10.

Continuous with an edge of the housing 18 adjacent to the slot 30 is acurved airflow catch 32. This airflow catch 32 is a partition or sheetcurving upwardly and toward the opening 20 in the housing 18. Theairflow catch 32 is also positioned in the path of incoming airflow. Thejuxtaposition of the vane 26 and airflow catch 32 forms a flow path orpassage between the vane 26 and airflow catch 32 toward the exit opening30. Part of the airflow 22 a goes directly into this flow path, whilepart 22 b is diffused by circulation along the airflow catch and theninto the flow path. This redistributes airflow to the edges for unifyingthe current velocities.

The hinge point 28 of the movable vane 26 is positioned so that gravitynormally biases the vane 26 toward the airflow catch 32. Other methodsof biasing the vane 26 toward the airflow catch 32 are by springs orweights which impose a comparable biasing load to that of gravity. If noairflow is flowing through the ceiling vent 10, then the vane 26 is in aclosed position 34 in contact with the airflow catch 32. When airflowmoves into the vent 10 from a source, the force of moving airflow movesthe vane 26 away from the airflow catch 32. Depending on the velocity ofthe airflow, the vane 26 will move to a fully open position 36 or to anyintermediate position 38 between fully open 36 and closed 34. The curvedshape of the vane 26 redirects airflow as it flows through the vent 10for laminar flow along the ceiling.

The distance between the bottom edge of the movable vane 26 and thecurved surface of the airflow catch 32 defines an opening 40 of variablewidth through which airflow exits the vent 10 to the room. The width ofthe opening 40, as determined by the extent of deflection of the curvedvane 26 in response to the force of inflowing airflow, regulates thevelocity of outflowing airflow. Not only is the velocity of outflowingairflow regulated by the vent 10, but the outflowing airflow is directedby the interaction of the concave side of vane 26 and convex side ofairflow catch 32 in a laminar flow along the ceiling of the room. Asnoted in the figures, the concavity of the vane 26 and the convexity ofthe airflow catch 32 are continuous along the passage sides of therespective vane and catch and up to the opening 40.

The airflow catch 32 diffuses and disperses the current of airflow thatenters the ceiling vent 10, especially the airflow that enters at lowerlevels in the current, such as at 22 b. The airflow catch 32 splits thisairflow off and circulates it within the plenum and disperses itlaterally, as depicted by dashed line 22 b. The curved configuration ofthe airflow catch 32 generates a circular flow path within a forwardportion 35 of the plenum, and then upward to the primary flow path 22 a.The airflow that is thus circulated by the airflow catch 32 rejoins theupper level current of airflow 22 a, is redirected by the movable vane26, and exits the vent in a generally horizontal direction along the topof the room. The airflow catch 32, by dispersing airflow laterallywithin the vent 10 makes the velocity of outflowing airflow constantacross the cross section of outflowing airflow instead of faster at thecenter of the outflow than at the edges. Further, airflow flow rates areincreased by this homogenization of outflowing air.

In the embodiment of FIG. 1 the airflow measurement system comprises acalibrated scale 54 attached to the end plate of the vent housing suchthat when the vane 36 moves in response to airflow through the plenum ofthe vent and out the second opening the tip 56 of the vane indicates onthe calibrated scale the amount of air that is flowing out the bottom ofthe vent. The system can subsequently be calibrated to distribute apredetermined amount of airflow into a room. For example, one method ofaccomplishing this would be to adjust the hinge 28 to stop at a certainset point at which a prescribed amount of airflow would enter the room.The airflow measurement system 54 can comprise a wide variety of systemsthat are known in the art. Airflow measurement systems generally includethe illustrated calibrated scale attached to the vent housing, a similarcalibrated scale attached to the vane such that, when the vane moves inresponse to airflow, a separate stationary pointer points to the airflowlevel on the calibrated scale, or any variety of digital or mechanicalairflow measurement systems.

FIG. 2, illustrates the vent 10 comprises a housing 18 that defines achamber 16 through which airflow may pass from the plenum source intothe room. FIG. 2 illustrates an embodiment of the airflow measurementsystem 54 comprising a calibrated scale attached to the vent housing.The airflow measurement system can be attached in a wide variety ofpositions on the vent housing including on the airflow catch 32, themoveable vane 36, the endplate of the vent housing 56, or any locationwhere it functions to measure airflow out of the ceiling vent.

The housing 18 contains an inlet opening 20 for supplying airflow to thechamber 16. Coupled to the inlet opening 20 are means 24 for attaching aconduit connecting the vent 10 to the plenum source. In the preferredembodiment, these means are a sleeve 24. Hingedly attached to thehousing 18 within the chamber 16 is a vane 26 which may rotate about arotational axis 28 and is positioned in the intended flow path ofairflow 22 a and 22 b entering the chamber 16 through the inlet opening20. The vane 26 exerts a deflecting resistance against the enteringairflow 22 a and 22 b which causes rotation of the vane 26 to a variabledegree in response to the velocity of the entering airflow 22 a and 22b. The vent 10 also comprises an outlet opening 30 within the housing18. This outlet opening 30 is positioned to receive airflow from thevane 26 and its opening size varies with the degree of rotation of thevane 26 in response to changing velocities of the entering airflow 22 aand 22 b. The outlet opening 30 is sufficiently small to provide achange in velocity to airflow as it exits the outlet opening 30. Theinvention also comprises means 32 associated with the vane 26 and outletopening 30 for directing airflow and causing initial laminar flow ofairflow exiting the outlet opening 30. In the preferred embodiment,these directing means 32 define an airflow catch 32.

To illustrate how this ceiling vent 10 tends to maintain constant theairflow throw of airflow currents of varying velocities, comparison witha vent of fixed aperture is useful. High-velocity airflow moving throughan aperture of fixed width will accelerate as it travels through theaperture. Thus, not only does the airflow enter the vent at highvelocity, but it is accelerated as it exits. Low-velocity airflow movingthrough the same aperture may accelerate as it moves through theaperture as well, but the acceleration will be less than that of thehigh-velocity airflow. Thus, the difference in velocities of thehigh-velocity airflow and low-velocity airflow is increased after movingthrough the fixed aperture.

In contrast, the difference in velocity of high-velocity airflow andlow-velocity airflow decreases after moving through a variable aperturethat is responsive to the flow rate of airflow. Acceleration of thehigh-velocity airflow through the variable aperture will be less than itwould have been through a fixed aperture because the aperture will widenin response to the force exerted by the high-velocity airflow againstthe movable vane 26. A limiting flange 37 blocks further movementrearward and sets the maximum size of the outlet. Also, acceleration ofthe low-velocity velocity airflow through the variable aperture will bemore than it would have been through a fixed aperture because theaperture will narrow in response to the lower force exerted by thelow-velocity velocity airflow against the movable vane 26. Thus, aceiling vent 10 with a movable vane 26 to vary the aperture throughwhich airflow exits to the room, tends to maintain a more constantvelocity of exiting airflow and, hence, a more constant airflow flowthrow.

While there is shown and described the present preferred embodiment ofthe invention, it is to be distinctly understood that this invention isnot limited thereto, but may be variously embodied to practice withinthe scope of the following claims. From the foregoing description, itwill be apparent that various changes may be made without departing fromthe spirit and scope of the invention as defined by the followingclaims. For example, although the disclosure refers to the vane being ina generally closed position when airflow is not flowing through thevane, the generally closed first position is the ideal position for thevane to be in when no airflow is flowing through the system. The firstposition is not required to be completely closed and is the relativedescription of the vane in the position without airflow flowing throughthe vent housing.

1. An improved ceiling vent for dispersing airflow from an airflowgenerated by a ventilation system into a room in laminar flow withrespect to a ceiling of said room, wherein said vent comprises: a venthousing configured to be mounted in a ceiling, wherein said vent housingcomprises a top, a bottom, a first side, a second side, a third side,and a forth side, wherein said first side and said second side aregenerally opposite, wherein said third side and said fourth side aregenerally opposite, wherein said vent housing defines a plenum on aninterior of said housing, wherein said vent housing comprises at leasttwo openings, wherein said openings comprise at least one first openingin at least one of said first side, said second side, said third side,or said fourth side of said vent housing for permitting inflow of saidairflow from said ventilation system into said plenum, wherein saidopenings comprise at least one second opening in said bottom side ofsaid vent housing for permitting said airflow to flow from said plenuminto said room; a vane comprising a concave curvature along its length,wherein said vane comprises a first end and a second end, wherein saidfirst end of said vane is hingedly attached to said interior of saidvent housing to form a movable side of said second opening foradjustment of said width of said opening and being positioned to receiveinflow of airflow into said plenum, wherein said vane is configured andpositioned such that when said ventilation system is not generatingairflow said vane is biased to generally close said second opening,wherein said vane is configured such that when airflow is flowing fromsaid first opening toward said second opening said airflow moves saidvane such that said airflow flows from said first opening through saidsecond opening, wherein said vane is configured to regulate said amountof airflow from said first opening through said second opening such thatsaid position of said vane is reversibly responsive to said airflowagainst said concave curvature of said vane and into said plenum to varysaid size of said second opening with movement of said vane by saidairflow while maintaining a curved flow path which discharges saidairflow in laminar flow along said ceiling, wherein said vane stabilizesa velocity of airflow that flows out from said plenum through saidsecond opening into said room, wherein said vane is configured to becalibrated to distribute a predetermined amount of airflow into saidroom; and wherein said improvement comprises an airflow measurementsystem attached to said ceiling vent, wherein said airflow measurementsystem is positioned and configured such that when said vane positionresponds to said airflow, said airflow measurement system indicates saidoutflow level of airflow out of said vent such that said ceiling ventcan be calibrated to distribute a prescribed amount of airflow into saidroom.
 2. The ceiling vent of claim 1 wherein said airflow measurementsystem comprises a calibrated scale comprising airflow measurementindicia, wherein said calibrated scale is positioned and configured suchthat when airflow flows through said ceiling vent, said calibrated scaleindicates said amount of said outflow of airflow out of said secondopening.
 3. The ceiling vent of claim 2 wherein said calibrated scale ispositioned such that when said airflow moves said vane and flows throughsaid second opening, said vane points to one of said airflow indicia onsaid calibrated scale to indicate said airflow out of said secondopening.
 4. The ceiling vent of claim 1 wherein said ceiling ventcomprises an airflow catch attached to said housing, wherein saidairflow catch comprises a generally circular sheet continuous with anedge of said vent housing at said second opening, wherein said airflowcatch is configured and positioned to partition said airflow from saidfirst opening to said second opening to facilitate mixing of saidairflow flowing into said plenum.
 5. The ceiling vent according to claim4 wherein said airflow catch is in a generally curved shape andconfigured to generate a circular flow path of airflow within saidplenum to facilitate mixing of airflow flowing into said plenum.
 6. Theceiling vent according to claim 4 wherein said airflow catch comprisesan extension of said vent housing.
 7. The ceiling vent according toclaim 1 further comprising means for biasing said movable vane towardsaid generally closed position such that said vane is configured to becalibrated such that when airflow is flowing through said ceiling vent,said vane can be calibrated to define said amount of airflow flowing outof said second opening.
 8. The ceiling vent according to claim 7 whereinsaid means for biasing said movable vane toward said vent housingcomprises a spring or a weight attached to said movable vane andconfigured for biasing said movable vane toward said generally closedposition.
 10. The ceiling vent according to claim 1 wherein said secondopening comprises a slot in said bottom wall of said vent housing. 11.The ceiling vent according to claim 1 wherein said movable vane formsone side of a narrowing passage having a concave curvature extending tosaid second opening for directing said outflow of airflow from said ventin laminar flow along said ceiling of said room to stabilize airflowthrow said ceiling vent.
 12. The ceiling vent according to claim 10wherein said airflow catch comprises an edge of said bottom wall and anedge of said slot, wherein said airflow catch curves generally upwardand toward said first opening, wherein said airflow catch forms agenerally circular structure such that said airflow catch and saidmovable vane are configured to form a generally circular airflow paththrough at least a portion of said ceiling vent when said airflow isflowing through said ceiling vent.
 13. The ceiling vent according toclaim 1, wherein said airflow measurement system is attached to at leastone of said movable vane or said vent housing.
 14. An improved ceilingvent for dispersing airflow from an airflow generated by a ventilationsystem into a room in laminar flow with respect to a ceiling of saidroom, wherein said vent comprises: a vent housing configured to bemounted in a ceiling, wherein said vent housing comprises a top, abottom, a first side, a second side, a third side, and a forth side,wherein said first side and said second side are generally opposite,wherein said third side and said fourth side are generally opposite,wherein said vent housing defines a plenum on an interior of saidhousing, wherein said vent housing comprises at least two openings,wherein said openings comprise at least one first opening in at leastone of said first side, said second side, said third side, or saidfourth side of said vent housing for permitting inflow of said airflowfrom said ventilation system into said plenum, wherein said openingscomprise at least one second opening in said bottom side of said venthousing for permitting said airflow to flow from said plenum into saidroom; a vane comprising a concave curvature along its length, whereinsaid vane comprises a first end and a second end, wherein said first endof said vane is hingedly attached to said interior of said vent housingto form a movable side of said second opening for adjustment of saidwidth of said opening and being positioned to receive inflow of airflowinto said plenum, wherein said vane is configured and positioned suchthat when said ventilation system is not generating airflow said vane isbiased to generally close said second opening, wherein said vane isconfigured such that when airflow is flowing from said first openingtoward said second opening, said airflow moves said vane such that saidairflow flows from said first opening through said second opening,wherein said vane is configured to regulate said amount of airflow fromsaid first opening through said second opening such that said positionof said vane is reversibly responsive to said airflow against saidconcave curvature of said vane and into said plenum to vary said size ofsaid second opening with movement of said vane by said airflow whilemaintaining a curved flow path which discharges said airflow in laminarflow along said ceiling, wherein said vane stabilizes a velocity ofairflow that flows out from said plenum through said second opening intosaid room, wherein said vane is configured to be calibrated todistribute a predetermined amount of airflow into said room; an airflowcatch attached to said housing, wherein said airflow catch comprises agenerally circular sheet continuous with an edge of said vent housing atsaid second opening, wherein said airflow catch is configured andpositioned to partition said airflow from said first opening to saidsecond opening to facilitate mixing of said airflow flowing into saidplenum; wherein said airflow catch and said movable vein are configuredto form a generally circular airflow path of air flowing from said firstopening through said vent housing; and wherein said improvementcomprises an airflow measurement system attached to said ceiling vent,wherein said airflow measurement system is positioned and configuredsuch that when said vane position responds to said airflow, said airflowmeasurement system indicates said outflow level of airflow out of saidvent such that said ceiling vent can be calibrated to distribute aprescribed amount of airflow into said room.
 15. The ceiling vent ofclaim 14 wherein said airflow measurement system comprises a calibratedscale comprising airflow measurement indicia, wherein said calibratedscale is positioned and configured such that when airflow flows throughsaid ceiling vent, said calibrated scale indicates said amount of saidoutflow of airflow out of said second opening.
 16. The ceiling vent ofclaim 15 wherein said calibrated scale is positioned such that when saidairflow moves said vane and flows through said second opening, said vanepoints to one of said airflow indicia on said calibrated scale toindicate said airflow out of said second opening.
 17. The ceiling ventaccording to claim 14, wherein said airflow measurement system isattached to at least one of said movable vane, said vent housing, orsaid air catch.
 18. The improved ceiling vent according to claim 14further comprising means for biasing said movable vane toward saidgenerally closed position such that said vane is configured to becalibrated such that when airflow is flowing through said ceiling vent,said vane can be calibrated to define said amount of airflow flowing outof said second opening.
 19. An improved ceiling vent for dispersingairflow from an airflow generated by a ventilation system into a room inlaminar flow with respect to a ceiling of said room, wherein saidceiling vent comprises: a vent housing configured to be mounted in aceiling, wherein said vent housing defines a plenum on said interior ofsaid housing, wherein said vent housing comprises at least one firstopening for permitting inflow of airflow from said ventilation systeminto said plenum, wherein said vent housing comprises at least onesecond opening for permitting outflow of airflow from said plenum intosaid room; and an airflow catch attached to said housing, wherein saidairflow catch comprises a generally concave curvature continuous with anedge of said vent housing at said second opening such that said airflowcatch is positioned and configured to diffuse a part of said inflow ofairflow from said first opening; and a vane comprising a concavecurvature along its length, wherein said vane comprises a first end anda second end, wherein said vane is hingedly attached to said interior ofsaid vent housing to form a movable side of said second opening foradjustment of said width of said opening and being positioned to receivesaid force of said inflow of airflow into said plenum, wherein said vaneis configured and positioned such that when said ventilation system isnot generating airflow said vane is biased to close said second opening,wherein said vane is configured such that when airflow is flowing fromsaid first opening toward said second opening said airflow moves saidvane such that said airflow flows from said first opening to said secondopening, wherein said vane is configured to regulate said amount ofairflow from said first opening through said second opening such thatsaid position of said vane is reversibly responsive to said force ofsaid inflow of airflow against said concave curvature of said vane andinto said plenum to vary said size of said second opening with movementof said vane by said force while maintaining a curved flow path whichdischarges in laminar flow along said ceiling, wherein said vanestabilizes a velocity of airflow that flows out from said plenum throughsaid second opening into said room, wherein said vane is configured tobe calibrated to distribute a predetermined amount of airflow into saidroom; and a means for biasing said movable vane toward said generallyclosed position such that said vane is configured to be calibrated suchthat when airflow is flowing through said ceiling vent, said vane can becalibrated to define said amount of airflow flowing out of said secondopening; and wherein said improvement comprises an airflow measurementsystem attached to said ceiling vent and positioned and configured suchthat when said vane position responds to said force of said inflow ofairflow, said airflow measurement system indicates said outflow level ofairflow out of said vent such that said ceiling vent can be calibratedto distribute a prescribed amount of airflow into said room, whereinsaid airflow measurement system comprises a calibrated scale comprisingairflow measurement indicia, wherein said calibrated scale is positionedand configured such that when airflow flows through said ceiling vent,said calibrated scale indicates said amount of said outflow of airflowout of said second opening by pointing generally to one of said indiciaon said calibrated scale.
 20. The improved ceiling vent of claim 19wherein said means for biasing said movable vane toward said venthousing comprises a spring or a weight attached to said movable vane andconfigured for biasing said movable vane toward said generally closedposition.